White Lupin (Lupinus albus L.) is a traditional legume crop in Ethiopia that can playrncomplementary or alternative roles as sources of organic fertilizers to replenish nitrogen depletedrnsoils in farming systems as it forms symbiotic associations with soil bacteria that have atmosphericrnnitrogen fixation and other plant growth promoting abilities. This study was aimed to investigaternthe diversity and symbiotic effectiveness of rhizobia and rhizobacteria on growth and productionrnof white lupin (Lupinus albus L.) from major producing areas of the country. A total of 100rnbacterial isolates were obtained from the root nodules of White lupin and characterized based onrntheir phenotypic, biochemical and plant growth promoting characteristics using various standardrnmethods. Accordingly, 39 isolates were confirmed as rhizobia on the basis of presumptive andrnauthentication tests. These rhizobial isolates showed wide diversity in their symbiotic and culturalrncharacteristics as well as heterotrophy, such as C and N-substrates utilization, tolerance to metalrntoxicity, antibiotics, pH, salt and temperature. Moreover, some of the isolates showed interestingrnPGP traits (IAA, siderophore and HCN production, P solubilization and antagonistic activityrnagainst Fusarium oxysporum) which can make them prior candidates for the production ofrninoculants for enhancing White lupin production in the country. Furthermore, the total of 136rnphosphate solubilizing bacterial isolates were obtained from rhizospheric soils of White lupinrnproducing area of the country and 40 effective phosphate solubilizing bacterial isolates werernselected on the basis of their solubilization index (SI). The phosphate solubilizing bacterial isolatesrnshowed variations in their cultural characteristics, doubling times, Gram reactions and C and Nsourcesrnutilization patterns. Quantitative estimation of phosphate solubilizing efficiency of thernphosphate solubilizing rhizospheric bacterial isolates on different inorganic phosphate sourcesrnshowed that some of the isolates have better solubilization potential of tricalcium, aluminum andrniron phosphates in Pikosvikya broth upon 5 days of incubation. In addition, they showed goodrniirntricalcium phosphate solubilization potential under different stress conditions, such as various saltrnconcentrations, pH and temperature ranges and most of them showed multiple plant growthrnpromoting characteristics. Furthermore, three rhizobial and two phosphate solubilizingrnrhizospheric bacterial isolates that showed better relative symbiotic effectiveness, plant growthrnpromoting features, stress tolerance and heterotrophic competence were selected to study the effectrnof single and co-inoculation on the growth and nodulation of the White lupin under greenhousernand field conditions. Accordingly, co-inoculated white lupin plants resulted in higher nodulernnumber, nodule and shoot dry matter accumulation, percent nitrogen and improved relativernsymbiotic effectiveness than single rhizobial inoculation, and N-fertilized plants on sand and soilrncultures under greenhouse conditions. Similarly, inoculation of White lupin plants either with thernselected rhizobial isolates alone or co-inoculation of rhizobial and phosphate solubilizingrnrhizospheric bacterial isolates showed improved performance on the nodulation, growth and yieldrnof the crop compared to the negative control under field conditions. In general, the present studyrnshowed that Ethiopian soils contain symbiotically effective White lupin rhizobia and efficientrnphosphate solubilizing rhizospheric bacteria with multiple plant growth promoting traits tornenhance growth and production of the crop under natural conditions. However, repeated testsrnshould be carried out on different field conditions in order to use these rhizobial and phosphaternsolubilizing bacterial isolates for inoculant production.